

a = [1,2,3,4,5,6]
b = [5,6,7,8]
c = []
d = a + b

print(list(set(d)))  # [1, 2, 3, 4, 5, 6, 7, 8]
a1 = [1,2,3] + [4,5,6,]
print(a1)  # [1, 2, 3, 4, 5, 6]

for i in a:
    if i not in b:
        b.append(i)
print(b)    # [5, 6, 7, 8, 1, 2, 3, 4]

